Lubricants containing fatty acid esters of saccharides



. LUBRICANTS CONTAINING FATTYACID ESTERS OF SACCHARIDES Arnold J. Morway, Clark, and Walter E. Waddey, Westfield, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Mar. 28, 1958, Ser. No. 724,524

7 Claims. (Cl. 252-405) This invention relates to lubricating compositions. Particularly, it relates to lubricating oil compositions which are thickened with an ester of a saccharide and a high molecular weight monocarboxylic acid.

It has been found that esters of disaccharides and high molecular weight fatty acids can be dispersed in lubricating oils to form semi-fluid greases having excellent stability against separation. Furthermore,-the use of these esters as thickeners makes possible the preparation of non-metallic lubricants and because of their no'npoisonous effect they may be used in those applications where a nonpoisonous lubricant is required. For example, .such ester thickeners may be used to prepare lubricants for use in food handling equipment such as dough mixers, conveyors, bottling, packaging and canning equipment. They may also be used in those applications where an ash-less lubricant is desired. It has been porated.

The disacchan'de portion of the ester is selected from the group consisting of sucrose, maltose, lactose and cellobiose. The monocarboxylic acid portion of. the ester can be derived from fatty acids containing 12 to 32, e.g. 16 to 24 carbon atoms. This includes naturally-occurring or synthetic, substituted and unsubstituted, saturated and unsaturated fatty acids. Examples of such acids include palmitic, stearic, dihydroxy s'tearic, :behenic, montanic, linolinic, linoleic, arachidic, ricinol'eic, oleic, hydrogenated fish oil, tallow acids, etc.

The esters which can be used as thickeners will include the mono-, diand tri-esters. Specific examples of these esters include: sucrose mono-stearate, sucrose distearate, sucrose tristearate, maltose dipalmitate, maltose monolaurate, maltose dimelissate, cellobiosemonooleate, su-

crose monotallowate, etc. Particularly preferred because of their commercial availability in large quantities are the sucrose mono and distearatel r Semi-fluid greases may be prepared by dispersing 3 to 40, e.g. 5 to 30 wt. percent of the ester in a lubricating oil by heating the ester and oil mixture until the ester dissolves in the oil under stirring. This will generally occur at about 280 to 320 F. The composition is then allowed to cool without stirring, whereupon a smooth, homogeneous stable semi-fluid grease results.-

2,944,024 Patented July 5, 1960 and dispersed by slight heating; or a lubricating oil dispersion of the ester may be added to other greases; or the other thickeners may be added or formed in the lubricating oil dispersion of the ester.

A particularly desirable material fo'r use with the ester thickeners are the alkaline earth metal (e.g. calcium, barium, strontium) salts of C to C fatty acids (acetic, propionic, butyric, etc.). Calcium acetate is particularly preferred for this purpose, since it will not only make a high dropping point solid grease, but will also impart considerable anti-wear and extreme pressure properties to the ester-containing lubricant. While the metal salts mentioned above may be added to the ester thickened lubricant in the form of an aqueous solution followed by dehydration, it is generally more desirable to form the alkaline earth metal salt in situ in the ester and oil mixture. This is readily accomplished by the reaction of an alkaline earth metal base, e.g. lime, with the desired acid, e.g. acetic acid or its anhydride. The mixture may or may not be externally heated depending upon what salt is formed and whether or not it is desired in the form of a hydrate. For example, if the salt formed is calcium acetate and if a small amount of water is present and the temperature of reaction is maintained below about ISO-200 F. the dihydrate will form. Now if the same reaction mixture is heated above about 180-200 F. the monohydrate will form, while temperatures of about 300 F. will result in anhydrous calcium acetate. Either the hydrates or anhydrous form may be desirable depending upon the ultimate use. Thus, generally speaking, for low temperature operation the hydrates will result in the greatest thickening eiiect while the anhydrous form will have less thickening effect but will be more desirable for high temperature use. Usually about 5 to 40 wt. percent, e.g. 10 to 35 wt. percent of the alkaline earth metal salt may be advantageously used in the ester thickened oil.

The lubricating oil used in the compositions of the invention may be a mineral lubricating oil, a synthetic lubricating oil, or mixtures thereof. Synthetic lubricating oils which may be used include esters of dibasic acids (e.g. di-Z-ethyl hexyl sebacate); esters of glycols (e.g. C Oxo acid diester of tetraethylene glycol); complex esters (e.g. the complex ester formed by reacting one mole of sebacic acid with two moles'of tetraethylene glycol and two moles of Z-ethyl-hexahoic acid); formals, silico'nes, carbonates, polyglycols and other synthetic lubricating oils known in the art.

Various other additives may also be added to the lubricating composition in amounts of about 0.1 to 10.0 weight percent, based on the totalweight of the composition. Examples of such additives include: detergents such as, calciumpetroleum sulfonate; corrosion inhibitors such as sorbitan monooleate; pour depressants; dyes; still other grease thickeners and the like.

The invention will be further understood by the' following examples which include preferred embodiments of the invention.

Example I 18.0 wt. percent of sucrose mono-stearate was added to 82.0 wt. percent of a mineral oil having a viscosity of 55 SUS at 210 F. This mixture was then heated V V V 2,944,024 r while stirring to 300 F. in order to disperse the sucrose iorm, homogeneous, having an opaque appearance and an unworked ASTM penetration at'77 Ref 400 mm./-10.

' 7' V Example ll Example I was repeated, but using sucrosedistearate in initiated until the temperature reached 220' F., at which point 'a sample was taken. The remainder of the com position was heated to 320 "F. to completely dehydrate the calcium acetate, followed by cooling to 200 F. where phenyl-u-naphthylamine was added. then cooled to room temperatures.

The compositions prepared above. and their physical characteristics aresummarized in. the following table:

place of sucrose monostearate. V V 10 TABLE 7 Composition and properties of examples III IV A 3 1 -11 320 F 320 F 220 F. V szo rl' Composition (wt. percent) Sucrose monostearate- Sucrose distearate Glacial acetic acid.. Hydratedlime Phenyl wnaphthylamine 7 Mineral lubricating oil (558 38 at 210 F 82.0%--- Properties: 7 g 7 7 Appearance; Uniform, homogeneous,

' aque. Stay-putness Does not flow down inclined surface or V V separate oil. 1 Dropping Point, ,Semi-fluid F Q. V Penetration ASTM 77 F., "mm I10- Unworked Worked 60 strokes-- Worked 100,000 strokes..- Water solubility Excellent, 'smo0th,1uniform grease.

Excellent, smooth No grease uniform grease.

NormaHotr'piann Oxidation LubricatlonLile Hours (250" F.-10,000

Alnrcnflest Wgts. Carried Four-Ball Wear Test 1,800 r.p.m.10 Kg. 7 Load 75 C.1 hour) ScarSpot diavln 1 Eours to a 5 psi. drop in oxygen pressure. Material still lubricating when test wasdiscontinued.

a Auti-frictionBearing ManufacturersNation-alLubricating Grease Institute test machine. V

7 Example 111 7 .3

10.0 parts by weight (pf-sucrose distearate was dispersed in 55.6 parts by weight of a mineral lubricating oil having'a viscosity'of 55 SUS at 210 F. by heating and stir-- structure formed. The temperature of reaction rose to 180. .F. and stirring .was continued until the temperature began to drop. External heating was then initiated and the temperature raised to 220 F. Atthis point a portion {of the product was removed for testing. The balance of the grease was heated to 320 F. and then allowed to cool while stirring. At 200 F. on this cooling cycle, 1.0 part by weight of phenyl-a-naphthylamine was added to inhibit oxidation and the grease was allowed tofurther cool to room temperature.

Exa pl IV A grease was prepared in the samemanner as the "grease of' Example HI prepared at 320 F., except for differentproportions of ingredients and the use of the .monostearate in place of the .distearate. I v V 'For comparison purposes a lubricant was prepared usmg calcium facetate as the sole thickener, i.e. without the'ester. Thislubricant :was prepared as :follows:' 13.4

wt percent of hydrated limeand 65.6 wtipercent o'f a mlneral lubricating oil of 55 SUS viscosity at 2l0 F. was mixed to form an intimate slurry. Then 20.0 Wt.

percent of glacial acetic acid was slowly added 'Vwhile Stirring; the -.temperature to 7 -1 80KB H ri was As seen from the preceding table,Examples I and show that both the sucrose monoand distearate formed a semi-fluid or soft greases. Example III (22051 demonstrated that calcium acetate monohydrate :successfully further thickened the sucrose distearate-oil composition to a high melting point grease having good load-carrying ability, low wear and oxidation resistance. ExamplelIl. f

(320 F.) shows that the anhydrous calcium acetate, had

substantially the same efiect as .well as demonstrating that such greases'have a long lubricating life 'atelevatcjd temperatures. Example IV (320 F.) illustrates theme of anhydrous calcium acetate with sucrose monostearate- Thecomparison compositions A(220 F.) andA'(320f. I

F.) show the effect of calcium acetate monohydrateand anhydrous calcium acetate as .the sole thickening agent. Other esters of the invention may be used to prepare lubricants in the general manner of Example I. For .example, Example I can be repeated but using cellobiose trioleate inplace-of the sucrose -monost'earate. What is claimedis: i

. 1. -A lubricating grease composltion comprising a major a proportion of lubricating oil, about 5 to 30 .wt'. percent ,of an ester of one mole of a disaccharideand 1-10 3 moles r of a'Ci to C fatty acid and 5 to .40 wt. .percentf'of an alkaline earth metal salt bfa C 1 to C '-'fatty.acid.

V 2. A lubricating composition accordingjto claim ,1; wherein said ester is asucrose monoester of a C to C fatty acid.' f I V V 3. A lubricating composition according toJclaim 1,

wherein said'ester is a sucrose diester 10f a C .tolC' fatty acid.

4. A lubricating composition according "to claim 1,;

-j-wherein said ester is sucrose 'monostearat e.

5. A lubricating composition according to. claim 1, wherein said ester is sucrose-distearate.

structure.

6. A lubricating, composition according to claim 1; wherein said salt is calcium acetate. V a

7. A lubricating composition according, to claim 6, wherein said calcium acetate is anhydrous.

References Cited in the file of this patent UNITED STATES PATENTS 2,115,823 Miller et 111. V May 3, 1938 McLennan Mar. 18, 1947 Sproule et a1. Aug. 19, 1952 Clayton et a1 Jan. 18, 1955 FOREIGN PATENTS Great Britain Sept; 28, 1933 Great Britain Sept. 17, 1934 

1. A LUBRICATING GREASE COMPOSITION COMPRISING A MAJOR PROPORTION OF LUBRICATING OIL, ABOUT 5 TO 30 WT. PERCENT OF AN ESTER OF ONE MOLE OF A DISACCHARIDE AND 1 TO 3 MOLES OF A C12 TO C32 FATTY ACID AND 5 TO 40 WT. PERCENT OF AN ALKALINE EARTH METAL SALT OF A C2 TO C6 FATTY ACID. 